Polymeric foam is finding increasing application in the construction industry. However, under some conditions the foam may be subject to insect infestation, and particularly termite infestation. There is a need for methods of rendering polymeric foams resistant to insects.
U.S. Pat. No. 5,194,323 issued Mar. 16, 1993 and U.S. Pat. No. 5,270,108 issued Dec. 14, 1993, both assigned to AFM Corporation, disclose and claim polymeric foams suitable for construction purposes which have been treated with a borate compound to inhibit insect and particularly termite infestation. The patent does not teach or suggest that the insecticide could be added to the monomer prior to polymerization.
U.S. Pat. No. 5,704,172 issued Jan. 6, 1998, assigned to The Dow Chemical Company, teaches a rigid polymer foam having a plurality of grooves crossing in diagonal configuration which facilitates the application of insecticides to such rigid foam. The foam may be used for construction purposes. The patent teaches an external post fabrication application of insecticide and does not suggest adding the insecticide to the monomer prior to polymerization.
Chemical Abstracts of Japanese Kokai 10036549 A2 published Feb. 10, 1998, and Japanese Kokai 63254143 published Oct. 20, 1988 teach applying anti-termite agents to the exterior of foams. The abstracts do not teach or suggest incorporating the insecticides into a monomer used to prepare the polymer.
The Chemical Abstract of French Patent 2698632 published Jun. 3, 1994 teaches the production of very light weight foams, preferably polyurethanes having a density from 5 to 20 g/l. While the patent teaches polyurethanes are preferred it also teaches that the foam may comprise polystyrene, polyacrylates, and polycarbonates. The disclosure suggests the active substances are preferably introduced into the mixture before polymerization. However, examples 1 and 4 of the patent illustrate the invention using polystyrene foam. The active ingredient is not introduced into the monomer but rather is introduced into "a viscous but liquid styrene prepolymer which has been prepared by heating at 60.degree. C. for an unspecified period of time a mixture of 1000 g of styrene monomer, 1 g of benzoyl peroxide and 70 g of tributyl phosphate as a plastifier". MALATHION is added to the resulting prepolymer. The temperature is adjusted to 45.degree. C. and the mixture is stirred while nitrogen is bubbled through the mixture to obtain a foam having a specific weight of 12 g/l. On a fair reading of the patent disclosure in its entirety one would not conclude that the active ingredient is added to the styrene monomer but rather is added to a partially polymerized polymer. This teaches away from the subject matter of the present invention.
Chemical Abstracts of Japanese Kokai 63264670 A2 published Nov. 1, 1988 and Japanese Kokai 63159451 A2 published Jul. 2, 1988 teach impregnating polystyrene beads with boron compounds or with compounds selected from the group consisting of Phoixom, Fenitrothion, Cyanophos, Acephate and Prothiophos, respectively. The patents do not teach dissolving the active ingredient in the monomer prior to polymerization.
None of the above art discloses dissolving the insecticide in the monomer prior to polymerization.